Frequency and voltage control in microgrids: Modeling and simulations in islanded mode

Given the intermittent nature of renewable generation, in order to successfully accommodate it into electrical grid and to reduce the control burden on utility networks, the idea of smartly managing and controlling smaller subsystems - either continuously operating in isolation from utility networks or as an extension to existing power supply structures - has been a focus of extensive research for a decade and is lately receiving considerable commercial attention. The design, development and analysis of such microgrids demand the availability of dynamic models which are capable of reflecting the newly introduced control capabilities and which offer the flexibility of simulating the operation scenarios which have not been taken into account in traditional practices of power system analysis and design. This paper focuses on an implementation of secondary frequency control and the so called grid forming capability of converter based renewable generators. Commercial simulation software PSS®NETOMAC and PSS®SINCAL have been employed because of their widespread use among the network development professionals. These models can be used in a network development process, in stability studies, and in online dynamic security assessment systems, in order to assess the capability of microgrids in providing a reliable power supply under different operating conditions, and to evaluate their dynamic response and the effectiveness of proposed control strategies.